Per @jimgoodwin and @skearns64, users need to know which indices they have access to, or else they'll be blindly defining index patterns without any context.

We need to explore ways to solve this problem within the UI. Some suggestions are:

1. Provide typeahead functionality within the index-pattern text input. As you type, you can see a list of index patterns you match.
2. Provide a filterable and sortable list of all index patterns in a modal. As the user types in an index pattern in the modal, the list is filtered to show indices which match the pattern. This could be more useful if the user has a very large number of indices.